(a) Field of the Invention
The present invention relates to a novel quaternary ammonium phosphate compound and, more particularly, to a quaternary ammonium phosphate compound having the following formula 1 and which has an anticorrosive and a biocidal effect and an efficient method of preparing the same. 
In the above formula 1, R1 is a straight or a branched alkyl or aryl radical with 1 to 27 of carbon atom(s) free of xe2x80x94OH group and may contain hetero-atoms, and both of R2 and R3 are methyl groups or R2 and R3 are combined to form a heterocyclic compound with 4 to 6 of carbon atoms containing oxygen and nitrogen.
(b) Description of the Related Arts
A quaternary ammonium halide containing a quaternary ammonium salt as a parental core, particularly, a quaternary ammonium chloride has the advantages of having, a high biocidal effect and a low degree of surface tension and toxicity and hence, it is often used for the purpose of cleaning and sterilizing various household and industrial goods. And it is also widely used as an additive in wood preservatives, paints, industrial water-treating agents, cleansers and biocides because it is highly stable.
A quaternary ammonium halide is typically prepared by using the following reaction formula.
R1R2R3N+R4Xxe2x86x92R1R2R3R4NXxe2x80x83xe2x80x83Reaction formula 1
In the above reaction formula 1, R1, R2, R3 and R4 are independently alkyl or aryl radicals and X is a halogen compound.
Recently, quaternary ammonium chlorides, particularly, N-alkyl-N-benzyl-N-dimethyl ammonium chloride and N-dialkyl-N-dimethyl ammonium chloride have been the subject of many studies. They are disclosed in U.S. Pat. Nos. 3,919,143 and 3,910,866 as polymer hardening promoters, disclosed in U.S. Pat. No. 5,300,635 as surfactants for separation of RNA and disclosed in U.S. Pat. Nos. 5,290,805, 5,399,762, 5,561,187 and 5,567,372 as common biocides. U.S. Pat. No. 4,929,454 and Journal of American Wood Preservativer""s Association(1987) pages 331xcx9c348 by A. F. Preston disclose a technique for preserving wood by impregnating the quaternary ammonium chloride in the wood.
U.S. Pat. No. 4,521,412 discloses iodopropargylammonium salts having a pesticidal effect and a method of preparing the same, and U.S. Pat. No. 5,266,567 discloses halopropargylated cyclic quaternary ammonium compounds and a method of preparing the same.
But all the above-described compounds have a high biocidal effect in a water system, but as they release halogen compounds such as fluorine, chlorine, bromine and iodine, they are difficult to apply to corrosive metal substances such as carbon steels, cast irons, stain steels or coppers. Accordingly, U.S. Pat. No. 5,438,034 (1995) discloses a quaternary ammonium carbonate and a method of preparing the same, the quaternary ammonium carbonate having the following formula 5 and which has no metal coupler and which can be obtained easily to be used as a wood preservative. The method adopts directly a gaseous or solid carbon dioxide as a carbonic acid of a reactant. 
In the above formula 5, both R1 and R2 are alkyl groups with 8 to 12 of carbon atoms.
U.S. Pat. No. 5,399,762 (1995) discloses a quaternary ammonium hydroxide and a method of preparing the same, the quaternary ammonium hydroxide being used as a wood preservative. An aqueous solution containing 80% quaternary ammonium chloride is used as a starting material and the equilibrium of a reaction is shifted by raising a temperature to 40xcx9c90xc2x0 C. so that the quaternary ammonium hydroxide can be prepared. However, if the temperature is raised as in the above, a parental core of the quaternary ammonium salt undergoes a Hofmann elimination and rearrangement reaction when the parental core is exposed under a high-temperature alkaline condition so that a yellowish-brown oily olefin and amine compounds emitting an amine ordor are formed. The compounds are highly hygroscopic and difficult to separate. In addition, in drying the ammonium hydroxide, a considerable quantity of the compound is decomposed.
Moreover, all the above-described compounds have been developed and designed only as common biocides and except for the quaternary ammonium hydroxide, they are limited to a structure that a leaving group of a reactant are ion-bonded with the quaternary ammonium salt as an anionic conjugate of the compound
In another aspect, United Kingdom Patent No. 1,199, 015 (1968) and U.S. Pat. No. 4,252,662 (1981) disclose a method of introducing a phosphoric ester as an anionic conjugate. However, this method adopts the phosphoric ester as a reactant and is applied in the field of a base material of a high-pressure fluid. And U.S. Pat. No. 4,716,037 discloses a quaternary ammonium compound having an alkyl group with a terminal alcoholic group and which is used in hair conditioners for the purpose of lessening corrosion of stain steels.
It is an object of the present invention to provide a quaternary ammonium phosphate compound having the following formula 1 and which has both a strong anticorrosive effect on a wide range of metals and biocidal effect to be used in corrosive metal substances such as carbon steels, iron casts, stain steels, coppers, tinning steel plates and alumina by substituting a dihydrogen phosphate ion(H2PO4,) for a Cl ion from a quaternary ammonium chloride, and a method of preparing the same.
Particularly, a novel quaternary ammonium phosphate compound having the following formula 1 is characterized in that it has an ether group including an unshared electron pair to improve an anticorrosive characteristic greatly and to be able to form a nonoxidative anticorrosive membrane.
A first aspect of the present invention provides a quaternary ammonium phosphate compound having the following formula 1. 
In the above formula, R1 is a straight or a branched alkyl radical with 1 to 27 carbon atoms or aryl radical with 6 to 27 carbon atoms which does not contain xe2x80x94OH groups as substitutents on the carbon atoms, and may contain heteroatoms in the alkyl or aryl chain; and both of R2 and R3 are methyl groups or R2 and R3 are combined to form a heterocyclic compound with 4 to 6 carbon atoms containing oxygen and nitrogen.
R1 is preferably p-(xcex1,xcex1,xcex3,xcex3)-tetramethyl butyl phenoxy ethoxy ethyl group, and R2 and R3 are preferably methyl groups.
And R1 is preferably a tetradecyl group, and R2 and R3 are preferably morpholinium groups having the following formula 2.
The second aspect of the present invention provides a method of preparing a quaternary ammonium phosphate compound having the above formula 1 having the step of reacting a quaternary ammonium hydroxide having the following formula 3 with a phosphoric acid. 
In the above formula 3, R1, R2 and R3 are the same as defined above.
The quaternary ammonium hydroxide is preferably prepared by reacting a solid quaternary ammonium chloride having the following formula 4 with a metal hydroxide of 1.05xcx9c2.0 equivalents to the quaternary ammonium chloride in a solvent containing an alcohol with 1 to 4 of carbon atom(s) at 0xcx9c35xc2x0 C. 
In the above formula 4, R1, R2and R3 are the same as defined above.
The third aspect of the present invention provides a composition having an anticorrosive and a biocidal effect, containing a quaternary ammonium phosphate compound having the above formula 1.
A quaternary ammonium phosphate compound having the above formula 1 is prepared as follows.
Reaction formula 2
A quaternary ammonium chloride contains a N-benzyl group in a parental core of a quaternary ammonium salt and is preferably selected from the group consisting of N-dimethyl-N-[p-((xcex1,xcex1,xcex3,xcex3)-tetramethyl butyl phenoxy]ethoxy ethyl-N-benzyl ammonium chloride, a mixture of N-dimethyl-N-dodecyl-N-benzyl ammonium chloride, N-dimethyl-N-tetradecyl-N-benzyl ammonium chloride, N-dimethyl-N-hexadecyl-N-benzyl ammonium chloride and N-dimethyl-N-octadecyl-N-benzyl ammonium chloride, and 4-benzyl-4-tetradecyl morpholinium, chloride. The metal hydroxide contains a mono-, di- or trivalent metal, preferably a monovalent metal, and more preferably sodium or potassium.
A step for preparing the quaternary ammonium hydroxide is a typical equilibrium reaction so that the reaction can be optimized by changing the ratio of equivalents of reactants, solvents and conditions of the reaction. The step is preferably carried out in a solvent containing an alcohol with 1 to 4 of carbon atom(s), preferably an ethanol, and more preferably an anhydrous ethanol. When a mixture of N-dimethyl-N-dodecyl-N-benzyl ammonium chloride, N-dimethyl-N-tetradecyl-N-benzyl ammonium chloride, N-dimethyl-N-hexadecyl-N-benzyl ammonium chloride and N-dimethyl-N-octadecyl-N-benzyl ammonium chloride is used as a starting material, the content of water can be minimized and the yield can be maximized by using the solid mixture having been crystallized with a drying method such as a lyophilization method. The metal hydroxide is preferably 1.05xcx9c2.0 equivalents to the quaternary ammonium chloride. If less 1.05 equivalents, the reaction rate is decreased and if more 2.0 equivalents, decomposition reaction may occur. The reaction is performed at 0xcx9c35xc2x0 C. so that a Hofmann elimination and rearrangement reaction occurring under a high-temperature alkaline condition can be suppressed and the reaction can be finished within 8 hours. Therefore, a filtrate containing the quaternary ammonium hydroxide is not required to separate and can be used directly in the subsequent step so that the prior filtrate drying step, where a considerable quantity of the quaternary ammonium hydroxide is decomposed, can be omitted.
A reaction between a quaternary ammonium hydroxide and a phosphoric acid is a neutralization reaction and even if some heat is generated, another side reaction is not likely to occur and therefore a separate cooling step is not required. If the residual metal hydroxide remains in the solution, it reacts quickly with dihydrogen phosphate ions preferentially and can be extracted and removed easily in the form of a metal phosphate salt.
A quaternary ammonium chloride having the above formula 4 is added and dissolved at room temperature in an alcohol solvent with 1 to 4 of carbon atom(s). A small quantity of a metal hydroxide containing a mono-, di- or trivalent metal is admixed and the solution is agitated for 1xcx9c8 hour(s). As the reaction is proceeded, a metal chloride is precipitated and the solution becomes turbid. After the reaction ends, the solution is cooled at a low temperature of about 0xc2x0 C. and a white metal chloride is completely removed. Then a filtrate containing a quaternary ammonium hydroxide intermediate having the above formula 3 is obtained. A phosphoric acid of equivalents corresponding to those of the quaternary ammonium hydroxide intermediate and the residual metal hydroxide is added with a dropping funnel at room temperature and an acid-base reaction is proceeded. A metal phosphate is extracted and separated with a filter. Removal of the solvent from the obtained solution by drying gives an oily paste or a white powdery quaternary ammonium phosphate.